Generally, as shown in FIG. 1, at least one cutting insert 2 is fixed to a pocket portion 3 of a cutting tool body 1 using a fastening means (e.g., a bolt) in a cutting tool such as a milling cutter. The milling cutter has a rotational axis RA which defines a front-to-rear axial direction of the cutting tool body 1. As for the cutting insert 2 fixed to the cutting tool body 1, the position of the cutting insert 2 must be adjusted along an adjustment direction Y, which may be along the front-to-rear axial direction to achieve precise cutting and prevent excessive force from being applied to any one of the cutting inserts. To this end, there is provided a device 10 for finely adjusting the position of the cutting insert at a rear portion of the cutting insert 2.
As shown in FIG. 2, in a conventional cutting tool, the cutting insert 2 is fixed to a pocket portion 3 of a tool body using a means such as a bolt (not shown). The device 10 for finely adjusting the position of the cutting insert comprises a wedge 11 and a screw 12. The pocket portion 3 has a bottom surface with a screw hole 3b formed thereon into which the screw 12 is fastened. It also has a side wall with a surface 3a for closely contacting the wedge 11.
The wedge 11 has a larger width as it goes upward. It also has a screw hole at its central portion into which a head portion of the screw 12 is fastened. The screw 12 has threads at its upper and lower portions. The threads formed at the upper portion of the screw 12 are engaged with the threads formed in the screw hole of the wedge 11. The threads formed at the lower portion of the screw 12 are engaged with the threads formed in the screw hole 3b provided at the pocket portion 3.
In the above-described cutting tool, the wedge 11, along with its peripheral side surface 16, moves up and down along the cutting insert 2 and the close contact surface 3a of the pocket portion 3 according to the extent of fastening the screw 12 having central axis C1 while causing the cutting insert 2 to move forward and backward along the adjustment direction Y, thereby finely adjusting the position of the cutting insert 2. For example, when further tightening the screw 12 in a state where the screw 12 is already tightened, the wedge 11 moves down along with the screw 12, thereby finely moving the cutting insert 2 outwardly (i.e., along adjustment direction Y away from the close contact surface 3a). In FIG. 2, the close contact surface 3a forms an obtuse external angle α with adjustment direction Y, in cross-section of the pocket portion 3 containing central axis C1 and the adjustment direction Y.
When applying a pushing force to the cutting insert 2 by using the wedge 11 as described above, a repulsive force F against the pushing force is applied to the wedge since the cutting insert 2 is fastened to the pocket portion 3 of the tool body. As a result, a bending stress is applied at the screw 12. Thus, the screw 12 is resiliently bent towards the close contact surface 3a of the pocket portion 3. In such a case, when removing the cutting insert 2 fixed to the pocket portion 3 to replace or repair the cutting insert 2, the bending stress occurring at the screw 12 is also removed, thereby moving the screw 12 along with the wedge 11 towards the cutting insert 2 (i.e., forward).
When fixing a new cutting insert 2 in a state where the screw 12 and the wedge 11 are moved to a position ahead of their original positions, a problem occurs in that the new cutting insert 2 fails to be mounted in a right position. This is due to an interference of the wedge, which is moved to the position ahead of the original position. Thus, a fine adjustment must be made again after demounting the wedge and mounting the cutting insert.